timestamp.c is broken (probably by ecpg) in 7.4

I get the error message below when trying to 'make' current cvs:
gcc -O2 -Wall -Wmissing-prototypes -Wmissing-declarations -fpic -I../../../../src/interfaces/ecpg/include
-I../../../../src/include/utils-I../../../../src/include -D_GNU_SOURCE   -g  -c timestamp.c -o timestamp.o
 
In file included from ../../../../src/interfaces/ecpg/include/compatlib.h:7,                from
../../../../src/interfaces/ecpg/include/datetime.h:4,               from timestamp.c:14:
 
../../../../src/interfaces/ecpg/include/ecpglib.h:9: libpq-fe.h: No such file or directory
make[4]: *** [timestamp.o] Error 1

My config is:
./configure --prefix=/usr/local/pgsql --enable-integer-datetimes --with-openssl --with-pgport=5433

This is on a redhat 6.1 system.